Wavelength tunable filter device

Abstract

A wavelength tunable filter device has at least two optical fibers through which an optical signal is input or output; a wavelength selective element which the optical signal is input to and output from through a lens and which selects a wavelength; a mounting jig to which the wavelength selective element is fixedly secured; a rotating mechanism, having an ultrasonic motor and an encoder, for rotating the wavelength selective element; and a motor controller for controlling the ultrasonic motor for driving, wherein the mounting jig is rigidly mounted directly to a rotating shaft of the ultrasonic motor, and the amount of power that does not exceed the driving power necessary to cause the ultrasonic motor to start rotating from a stopped condition is intermittently applied to the motor controller.

What is claimed is:  
     
       1. A wavelength tunable filter device comprising: at least two optical fibers through which an optical signal is input or output; a wavelength selective element which said optical signal is input to and output from through a lens and which selects a wavelength; a mounting jig to which said wavelength selective element is fixedly secured; a rotating mechanism, comprising an ultrasonic motor and an encoder, for rotating said wavelength selective element; and a motor controller for controlling said ultrasonic motor for driving, wherein 
       said mounting jig is rigidly mounted directly to a rotating shaft of said ultrasonic motor, and  
       an amount of power that does not exceed the driving power necessary to cause said ultrasonic motor to start rotating from a stopped condition is intermittently applied to said motor by said motor controller.  
     
     
       2. A wavelength tunable filter device according to  claim 1 , wherein said wavelength selective element is a diffraction grating or a Fabry-Perot etalon element. 
     
     
       3. A wavelength tunable filter device according to  claim 2 , wherein said diffraction grating is a Fourier diffraction grating. 
     
     
       4. A wavelength tunable filter device according to  claim 1 , wherein said encoder in said rotating mechanism is an optical encoder that uses a semiconductor laser in a rotational position detection system. 
     
     
       5. A wavelength tunable filter device according to  claim 1 , wherein said output fiber includes a light detector, and said motor controller controls the rotational speed of said ultrasonic motor based on a light intensity signal detected by said light detector. 
     
     
       6. A wavelength tunable filter device according to  claim 1 , wherein at least two diffraction gratings are mounted on said mounting jig symmetrically about the rotating shaft thereof. 
     
     
       7. A wavelength tunable filter device according to  claim 1 , wherein said rotating mechanism, has a minimum rotational angular resolution of one hundred-thousandth revolution. 
     
     
       8. A wavelength tunable filter device comprising: at least two optical fibers through which an optical signal is input or output; a wavelength selective element which said optical signal is input to and output from through a lens and which selects a wavelength; a mounting jig to which said wavelength selective element is fixedly secured; a rotating mechanism, comprising an ultrasonic motor and an encoder, for rotating said wavelength selective element; and a motor controller for controlling said ultrasonic motor for driving, wherein said mounting jig is rigidly mounted directly to a rotating shaft of said ultrasonic motor, said mounting jig being disposed between-said ultrasonic motor and said encoder. 
     
     
       9. A wavelength tunable filter device according to  claim 8 , wherein said wavelength selective element is a diffraction grating or a Fabry-Perot etalon element. 
     
     
       10. A wavelength tunable filter device according to  claim 9 , wherein said diffraction grating is a Fourier diffraction grating. 
     
     
       11. A wavelength tunable filter device according to  claim 8 , wherein said encoder in said rotating mechanism is an optical encoder that uses a semiconductor laser in a rotational position detection system. 
     
     
       12. A wavelength tunable filter device according to  claim 8 , wherein at least two diffraction gratings are mounted on said mounting jig symmetrically about the rotating shaft thereof. 
     
     
       13. A wavelength tunable filter device according to  claim 8 , wherein said output fiber includes a light detector, and said motor controller controls the rotational speed of said ultrasonic motor based on a light intensity signal detected by said light detector. 
     
     
       14. A wavelength tunable filter device according to  claim 8 , wherein said rotating mechanism has a minimum rotational angular resolution of one hundred-thousandth revolution.